Size-dependent flight capacity and propensity in a range-expanding invasive insect

Area of Science:

• Ecology
• Entomology
• Evolutionary Biology

Background:

• Capital-breeding insects accumulate all adult resources during larval stages, making adult body size a proxy for energetic capacity.
• In species with flightless females, male flight ability is critical for mate-finding, influencing reproductive success and population dynamics.
• The invasive Lymantria dispar (L.), a capital breeder with flightless females, presents a model for studying male flight capacity and its ecological implications.

Purpose of the Study:

• To quantify male Lymantria dispar flight capacity and propensity in relation to morphological and physiological traits.
• To investigate how diet-mediated variation in body size affects male flight performance.
• To understand the implications of male flight characteristics for mate-finding, invasion dynamics, and conservation concerns.

Main Methods:

• Male Lymantria dispar were reared on diets with varying protein content to produce a range of body sizes.
• Fixed-arm flight mills were used to measure male flight capacity, including total flight distance and maximum speed.
• Morphological measurements such as wing length, relative thorax mass, and forewing aspect ratio were recorded.

Main Results:

• Wing length, relative thorax mass, and forewing aspect ratio were significant predictors of male flight distance and speed.
• Larger body size, achieved through higher protein diets, correlated with enhanced flight performance in male Lymantria dispar.
• These traits collectively influence the ability of males to locate mates, particularly at low population densities.

Conclusions:

• Male body size and associated morphological traits are key determinants of flight performance in Lymantria dispar.
• Enhanced male flight capacity is vital for mate-finding, influencing reproductive success and the invasive spread of Lymantria dispar.
• Findings are relevant to understanding population dynamics, Allee effects, and management strategies for invasive species and conservation concerns.